The objective is to help satisfy an important need, the need to know the biochemical nature of the different kinds of cells in the nervous system. Brain function depends on the interplay of diverse kinds of cells, grandly entangled with each other. The admixture of the many cell types and the fact that the functional state differs from cell to cell, and from moment to moment, means that macroscopic chemical approaches are limited in usefulness. On the other hand, an analytical methodology is available which has virtually unlimited sensitivity and which makes it possible to measure nearly any enzyme or metabolite in single nerve cell bodies, in nuclei of large neurons, and in other neuronal structures of similar size. It is the purpose of this project to exploit this analytical capability in the study of the nervous system. In some cases, single neurons or portions thereof are examined; in other cases, small groups of cells are studied. Specifically, the retinal layers offer an opportunity to separate for analysis subcellular regions from the same portion of a number of cells.